The present invention relates to a vehicle anti-theft apparatus that uses vehicle position information.
Japanese Laid-Open Patent Publication No. 11-091510 describes a conventional immobilizer system. The immobilizer system includes a transponder, which is incorporated in a portable device such as an ignition key, and an anti-theft apparatus, which is installed in a vehicle.
In the prior art, the ignition key is inserted in a key cylinder of a vehicle and turned to an ignition position. As a result, the anti-theft apparatus supplies the transponder with electromagnetic energy through radio waves, that is, in a non-contact manner. The transponder, which is activated by the electromagnetic energy, then transmits an ID code, which is stored in the key, as a radio wave having a predetermined frequency. An ID code is registered in the anti-theft apparatus. The anti-theft apparatus enables the engine to be started when the received ID code matches the stored ID code. When the two ID codes do not match, the anti-theft apparatus prohibits the starting of the engine. Accordingly, the starting of the engine is disabled when the ignition key is not authentic. This prevents the vehicle from being stolen.
The conventional anti-theft apparatus performs user authentication through the input of an authorization code when registering the ID code of the ignition key in the anti-theft apparatus. The input of the authorization code is requested to prevent an unauthorized user from registering an ID code. In the prior art, when the authorization code is authenticated and the ID code format of the ignition key matches the ID format set for the vehicle, the ID code of the portable device is registered as the registration ID code in the memory of the anti-theft apparatus. The ID code of the portable device is recorded in the vehicle anti-theft apparatus to enable the user to start the vehicle engine with the portable device. This also disables a third person from starting the engine and thus prevents the vehicle from being stolen.
However, in the conventional vehicle anti-theft apparatus, when a portable device having an ID code with a format matching the ID code format set for a vehicle is available for a third person who knows how to register the ID code, the third person may re-register the ID code in the vehicle anti-theft apparatus. Therefore, there is a possibility of the vehicle being used by the third person.